The present invention relates to fluid supply systems and more particularly, to fluid supply lines having flanged connections in turbine frame modules of jet engines.
In aircraft turbine and similar engines having supply lines for use in cooling and lubricating components of the engine, it is necessary to maintain the lines so that they are not pinched, twisted or ruptured, which would result in leakage of oil. Additionally, oil supply lines generally comprise many tube segments coupled together by flanges. Such flanges are brazed to the ends of the tubing and include holes so that contiguous flanges may be bolted together.
A problem which arises during assembly and disassembly of the tube segments is that excessive torquing of the flange bolts during assembly, or seizing of the bolts during disassembly, can twist the entire oil supply tube, yielding the tube and causing braze cracking at the hub attachment point between the flanges and the tube segments. The combination of braze cracking and transient vibratory response loading can result in crack initiation in the oil supply tube, leading to subsequent in-service tube failure.
A special anti-torque ratchet has been developed for assembly and disassembly of the tube sections to prevent this problem; however, such tools are expensive and inconvenient to use. Further, the number of ratchets that would be necessary in an aircraft assembly and disassembly environment would increase the expense and inconvenience, making their use even more undesirable.
Various clamps and mountings have been designed which are secured to the frame of associated equipment and are clamped to fluid lines to hold the lines in position relative to the frame and to each other. However, problems exist with such prior known clamps when utilized for an oil supply tube in the turbine frame module of a gas turbine engine. For example, the engine vibration is transmitted from the frame to the clamps to damage the oil supply tube as well as loosen the engagement between the clamps and tube. Tube vibration may also cause the brackets to become loose, and the vibration between the bracket and tube further damages the tube.
In addition, using a bracket which is mounted on the frame structure inhibits thermal expansion of the oil tube during engine operation. Typically, the oil tube and the frame module have different thermal expansion rates, causing the bracket to grow at the rate of the frame and not at the rate of the tube, thereby damaging the tube.
Furthermore, prior bracket designs do not torsionally restrain the hardware used to connect the oil supply tube flanges during assembly and disassembly of the tube segments. If a flange is not properly restrained during assembly and disassembly of the tube segments, the flange will twist, cracking the braze between the flange and the supply tube. Therefore, the need exists for a flange bracket that restrains rotational and axial movement of the oil supply tube during assembly and disassembly of the tube segments, and provides slight movement of the oil supply tube due to the differences in thermal expansion of the supply tube and the turbine frame module.